Fredd001

Good evening guys, I finally decided to post and ask for any feedback regarding this issue. As of a week ago I began to notice my 09 ISF started to feel slower than usual and the throttle-acceleration response has completely changed. Overall stock, just straightpipe after resonator and recently hit 80k miles.
1.Biggest thing I’ve noticed and hopefully the great Lexus gurus have seen before is that while let’s say doing 45mph in let’s say 5th gear @2000 rpms, then completely mashing the gas, It downshifts to 3rd gear @ let’s say 3000 rpms. Instead of a steady rpm rise, I get a hiccup, rising from 3000rpms to 3500rpms to(hiccup) back down to 3000 or 3200rpms and then riding again up to wherever the next shift point is.
2. Another thing it does is that after completely mashing the gas instead of downshifting immediately like it used to, it accelerates at its current gear for about 500-1000rpms then it downshifts. But even after downshifting it doesn’t nearly feel as fast as before.
I hope you guys understand what I mean. Besides that, car shifts great, always use premium gas, cleaned air filter. I’ve owned the car for about 8 months now put on about 10k miles with no issues until now. I’ll have to check the service record or ask the dealership but as of now I have no idea when the sparplugs were last replaced. While having some exhaust work done today I had the mechanic check the spark plugs he had easiest access to and he said it could use new plugs, the current ones weren’t shot but that I could use new ones soon. I never told him about my issue mentioned above by the way.

What do you guys think is going on here? Do I just need new spark plugs? Could the fuel pump be failing not supplying enough fuel throughout the demanding acceleration range? Overall it feels like I’ve lost a good amount of power and I’m starting to feel sad and pissed. All and any feedback is welcomed! Thank you very much.

isfvss

What does it do in manual mode and sports mode, any codes, gearbox oil level ??

lobuxracer

iTrader: (2)

If you have 80k on the original plugs (very possible) you just need to change them. If it doesn't respond to a plug change, then post back and tell us what it is doing. I'd bet on the plugs being tired. It normally shows up at WOT where you are experiencing issues.

Vitveet

Could quite possibly need/could use new transmission fluid. Despite no supposedly not needing to change the transmission fluid ever, some guys have changed it out around 80-100k miles and have had VERY good feedback from it...reporting much smoother up and downshifts, quicker automatic shifts, etc.
Would try the plugs first, then the transmission fluid if that doesn't work.
Good luck and let us know your finds/results!

V.

lobuxracer

iTrader: (2)

This has not been my experience. The only thing improving shifting in my car was setting the level correctly. When I did the pan drop, filter replace, and add 5.5 quarts of WS ATF after properly setting the level, nothing changed at all.

Fredd001

Thank you all for the feedback!

No codes
Its doing the same thing on Sports mode and manual just feels super slow.
How do we check the gearbox oil levels on our Fs?

I appreciate your input brother, as you mentioned its all happening under WOT, so I will definitely change the spark-plugs asap, i should go with the OEMs correct?
Also the mechanic recommended a fuel system flush or cleaning when changing the sparkplugs, he said there is some carbon deposits and it could use cleaning. Should i have them do that or will some seafoam or water on the vacuum lines do just as good?

I appreciate the input, after reading to never mess with the tranny fluid ive never even attempted, but if after changing plugs and all the issue persists ill look into checking all damn oil levels haha.

Ok ill definitely would like to have all fluids checked if the spark-plug change doesnt fix the issue.

Again thank you all for the help! I will be reporting back asap. Car was perfect and just in the last couple days is when WOT took a dive so lets hope is only spark plugs!

isfvss

If your plugs were stuffed it would happen all the time misfiring and throw codes, your cats could have collapsed or o2 sensors or maf or gearbox ecu but just change the plugs first good luck ( to many oars)

Fredd001

wouldnt any of that throw some codes lol? I have no codes at all, I will put the obd reader on it to double check. Car drives fine and accelerates like a regular car just WOT is way underpowered.

Joker4096

iTrader: (2)

Do a full tune up and reset the ecu. Then do some highway speed full throttle pulls. Have you been driving the car stop and go a lot lately?

Fredd001

thanks for replay and I plan on doing a tune up as soon as my spark plugs come in!
i do a lot of stop and go driving on a daily, I drive it hard on a daily actually. How does this factor in brotha?

I8ABMR

Plugs ....

mahcah

iTrader: (3)

You speaking from experience with the ISF or the Camaro?

lobuxracer

iTrader: (2)

You must have never had a 1980 Honda 750F with ND plugs that died above 6k rpm after only 600 miles. Ran like a top below 6k, but broke up miserably when trying to get to the 9500 rpm redline.

ultimase

From what I remember generally worn spark plugs will manifest themselves at higher rpm first, leave them in there long enough and you might get idle problems as well. In boost applications you closed the gap smaller and smaller until the misfire went away, it was kinda a give and take. You want a larger gap to get better combustion at idle or just off idle, but these big gaps wouldn't function at higher rpm and boost, so you wanted smaller gaps there. Only smaller gaps didn't get you the best idle.

isfvss

No had a K1, I hope his problem are only plugs.